A Lundell type rotating machine is a rotating machine which excites comb-like rotor magnetic poles with a field magnetomotive force. Through adjustment of the field magnetomotive force, a magnetic flux can be easily adjusted in accordance with a rotating speed and an output. Therefore, the Lundell type rotating machine has been traditionally used mainly for a power generator for automobiles. The Lundell type rotating machine is relatively small in size when included in such a small-sized power generator. In general, claw-like magnetic poles are often formed by forging. However, the claw-like magnetic poles, which are integrally formed by forging, supports all centrifugal force acting on claw portions thereof by yoke portions at the bottom of the claw-type magnetic poles. Therefore, a load thereon in terms of mechanical strength is large. Thus, when the size of the Lundell type rotating machine is increased in an axial direction, in particular, the claw-like magnetic poles cannot bear the centrifugal force. Hence, there is a mechanical restriction in the axial length direction. Moreover, in magnetical terms, when an axis of a rotor is increased in length, a magnetic path of the rotor is more likely to be magnetically saturated, thereby causing effective use of the field magnetomotive force to be difficult. For those reasons, the Lundell type rotating machine is difficult to design when, in particular, the axis thereof is to be increased in the axial length, and therefore is mainly used for small machines.
Moreover, each of the magnetic poles formed by forging is made of an iron ingot. Therefore, a surface thereof allows a large eddy current to flow therethrough, and due to generation of the eddy current on the surface, efficiency is lowered. For those reasons, the Lundell type rotating machine has been rarely used in the field of products such as large-sized power generators, hybrid cars, and electric automobiles, which require high output and high efficiency.
In order to overcome the above-mentioned problems, a method of retaining laminated magnetic poles by a non-magnetic ring to configure a magnetic path equivalent to that of each of the claw-type magnetic poles has been proposed (for example, see Patent Literature 1).
As another technology, a technology of retaining an iron core with a non-magnetic ring and embedding permanent magnets into the non-magnetic ring to increase an output has also been proposed (for example, see Patent Literature 2).